1. Field of the Invention
The present invention relates to a servomotor, and more particularly to a servomotor having a wire-saving serial output of servomotor identification information and encoded feedback control signals to improve the match control and misconnection of a diversified servomotor and a driver as well as the control of the servomotor.
2. Description of Prior Art
At present, a servomotor is operated, driven and controlled mainly by related information including motor rotor position, speed and rotating direction required by the servo optical encoder and the feedback driver, and thus a good design or a good control method for an optical encoder and its signal processing circuit can enhance the matching, the control, and the wiring cost between the motor and the driver.
The structure of a traditional servo optical encoder applied to a servomotor usually includes an optical transmitter, an optical receiver, a rotary coding disc, a fixed coding plate, a processing circuit and a mechanical body as disclosed in R.O.C. Pat. No. I232631, and the difference of a servo optical encoder from a general encoder resides on that the servo optical encoder uses the design of tracks on a coding disc 8 for outputting a phase change signal as shown in FIG. 1, in addition to providing a rotor operating signal (A, B, Z), wherein a stripe 81 corresponds to signals A, B, and tracks 82, 83, 84 correspond to phase change signals U, V, W, and a different quantity of magnetic pole rotors of a servomotor corresponds to a different distribution of phase change signals for the digital coding of a disc. Referring to FIG. 2, the digital coding of a disc corresponding to a servomotor having ten magnetic poles further provides a phase change signal (U, V, W), wherein the rotor operating signal (A, B, Z) provides related information including the feedback operating position, speed and loop number to facilitate an accurate control of the driver, and the phase change signal (U, V, W) feeds back the rotor magnetic field position before starting and provides the phase change strategy for the driver, and these signals vary with the quantity of magnetic poles of the servomotor according to the design of the coding disc and the distribution of the pattern.
Further, most of the signals of a prior art servo optical encoder are outputted in pairs as shown in FIG. 3, and a total of 14 wires including the power input is needed, wherein the phase change signal (U, V, W) mainly provides the positions of the magnetic poles of a motor rotor, so that the driver can rotate the motor in the same direction of the magnetic field, and thus the phase change signal (U, V, W) is usually provided before the operation of the motor starts. In other words, the transmission of phase change signals (U, V, W) in pairs through six transmission lines will be idled after the motor is started and operated normally, and thus such arrangement incurs an additional cost for installing the transmission line, and there is a need to save the wires and reduce the cost for the wiring requirement.
U.S. Pat. No. 5,684,373 mainly uses electronic components such as a timer and a multiplexer to send out the phase change signal (U, V, W) after the power is turned on for approximately several hundreds of milliseconds, and then after the signals are transmitted, the same transmission line is used to send out the rotor operating signal (A, B, Z) and feed back the required operating control related information to the driver. Therefore, only eight transmission lines are needed for transmitting signals, so as to save the wiring and lower the cost.
As servomotors become increasingly popular, there are different combinations of driver and motor for different occasions, and motors of different features have different control parameters to control the motors effectively. Particularly, related information for identifying the motor including rated speed, power, external look and geometric size are included into the transmitted signals of the servo optical encoder. With the transmission of such related information, the driver can correspond to the related motor parameters to facilitate the related controls of the motor. On the other hand, the driver also can determine whether or not the motor is matched to avoid a misuse by users. However, the information provided by the prior art servo encoder and the foregoing cited U.S. patent is insufficient, and does not provide additional motor identification related information. If it is necessary to use the general wiring output method adopted by the prior art servo optical encoder to provide additional motor identification related information, then the quantity of wires will be increased accordingly. Of course, the wiring and its cost will be increased as well. As to the foregoing cited U.S. patent that emphasizes on wire-saving, it is necessary to use more electronic components if additional motor identification related information is provided without installing additional wires. Regardless of adopting the processing circuit architecture and signal transmission control method for the wire-saving optical encoder according to the prior art servo optical encoder or the foregoing cited U.S. patent, these prior arts cannot cope with different changes without changing the current existing architecture.